This invention arose from efforts to meet user requirements in the application of heat exchanger systems to naval requirements, particularly with respect to installations on submarines. Heat exchangers are used for maintaining equipment in readiness for operation by warming liquid coolants, lubricating fluids, or fuel while an engine or other equipment is not operational. Such heat exhangers typically require utilization of an auxiliary pump for circulating the liquid, The operation of a pump might introduce undesirable pulsations to the circulated liquid which, in the case of a submarine, might be detected from the exterior of the vessel.
There are many other applications where liquid pulsations in a circulating system are undesirable or harmful. Liquid systems that include quick opening or closing valves also are subjected to pulsations which can be very severe, such as in water supply systems subjected to "water hammer". These pulsations, which travel substantially unimpeded throughout the entire liquid sytsem because of the inherent non-compressible nature of a liquid, can sometimes result in structural damage to the liquid system and attached structures.
The development of this system arose from the analogy between electronic circuits and liquid systems. It is well known in electronics that selected frequencies can be filtered by use of a coil and a capacitance wired parallel to one another through a common junction. In attempting to produce a simialr effect in a liquid system, a coil-like liquid path and a straight liquid path were combined along a common sound transmitting member. Because of its ready availability, an existing heat exchanger was modified both structurally and operationally during experimental development of the device. The available heat exchanger was utilized because it included a helical liquid path having relatively low back pressure. It has been found by further experimentation that the resulting apparatus produces new and unexpected reductions in pulsation amplitude through the liquid system over a wide range of monitored frequencies.